Light Emitting Element Having a Capping Layer on an Electrode, Light Emitting Device Having the Same and Method for Manufacturing the Same

Abstract

A light emitting element comprises a first electrode, a second electrode configured to transmitting light, an organic layer arranged between the first and the second electrodes, comprising a light emitting layer, and a capping layer arranged on the second electrode and made of a material with a higher refractive index than the refractive index of the material constituting the second electrode. The material constituting the capping layer comprises at least one selected from the group consisting of triarylamine derivative, carbazole derivative, benzimidazole derivative and triazole derivative.

The invention claimed is: 
     
       1. A light emitting device comprising:
 a plurality of light emitting elements, each of which comprises
 a first electrode; 
 a second electrode configured to transmit light; 
 an organic layer arranged between the first electrode and the second electrode and comprising a light emitting layer; and 
 a capping layer arranged on the second electrode and made of a material with a higher refractive index than the refractive index of the material constituting the second electrode and with a bandgap of 3.2 eV or higher, 
 
 wherein the material constituting the capping layer comprises at least one compound selected from the group consisting of a triarylamine derivative, a carbazole derivative, a benzimidazole derivative and a triazole derivative, 
 wherein the capping layer is arranged so that the second electrode is arranged between the organic layer and the capping layer, 
 wherein the light emitting elements are classified into a first light emitting element emitting red light, a second light emitting element emitting green light, and a third light emitting element emitting blue light, 
 wherein the thickness of the capping layer of the first light emitting element (d 1 +d 2 ), the thickness of the capping layer of the second light emitting element (d 1 ), and the thickness of the capping layer of the third light emitting element (d 2 ) satisfy the formula d 1 >d 2 , and 
 wherein the thickness of the capping layer of the first light emitting element (d 1 +d 2 ) is within 10% with respect to the sum of the thickness of the capping layer of the second light emitting element (d 1 ) and the thickness of the capping layer of the third light emitting element (d 2 ). 
 
     
     
       2. The light emitting device according to  claim 1 , wherein the material constituting the capping layer comprises a triphenylamine derivative. 
     
     
       3. The light emitting device according to  claim 1 , wherein the material constituting the capping layer comprises at least one compound selected from the group consisting of N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), 4,4′,4″-tris[(3-methylphenyl)phenylamino]triphenylamine (m-MTDATA), 1,3,5-tris[N,N-bis(2-methylphenyl)-amino]-benzene (o-MTDAB), 1,3,5-tris[N,N-bis(3-methylphenyl)-amino]-benzene (m-MTDAB), 1,3,5-tris[N,N-bis(4-methylphenyl)-amino]-benzene (p-MTDAB), and 4,4′-bis[N,N-bis(3-methylphenyl)-amino]-diphenylmethane (BPPM). 
     
     
       4. The light emitting device according to  claim 1 , wherein the material constituting the capping layer comprises at least one compound selected from the group consisting of 4,4′-N,N′-dicarbazol-biphenyl (CBP), 4′4′,4″-tris(carbazol-9-yl)-triphenylamine (TCTA), 2,2′,2″-(1,3,5-phenylene)tris-[1-phenyl-1H-benzimidazole] (TPBI), and 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ). 
     
     
       5. The light emitting device according to  claim 1 , wherein the thickness of the capping layer is in the range of 30 nm to 120 nm 
     
     
       6. The light emitting device according to  claim 1 , wherein the refractive index of the capping layer is 1.75 or higher when the wavelength of the light transmitting through the capping layer is in the range of 380 nm to 780 nm. 
     
     
       7. The light emitting device according to  claim 1 , wherein the extinction coefficient of the capping layer is 0.12 or lower when the wavelength of the light transmitting through the capping layer is in the range of 380 nm to 780 nm. 
     
     
       8. A method for manufacturing the light emitting device of  claim 1 , comprising:
 depositing the material constituting the capping layer onto the second electrodes of the first and the second light emitting elements, to form a first layer onto the second electrodes of the first light emitting element, and to form the capping layer onto the second electrode of the second light emitting element respectively; and 
 depositing the material constituting the capping layer onto the first layer and onto the second electrode of the third light emitting element respectively, to form the capping layer on the second electrodes of the first and the third light emitting elements. 
 
     
     
       9. The method for manufacturing the light emitting device according to  claim 8 , wherein the sum of the thickness of the capping layer of the second and the third light emitting element is substantially the same as the thickness of the capping layer of the first light emitting element.